This invention relates to the preparation of ethylidene diacetate (1,1-diacetoxyethane) by the application of carbonylation techniques to dimethyl ether and/or methyl acetate in the presence of hydrogen.
Ethylidene diacetate is a chemical intermediate of great commercial interest in view of its ready convertibility to a number of different tonnage chemicals of commerce. By one known conversion technique, ethylidene diacetate is readily transformed to vinyl acetate plus acetic acid; see Kirk-Othmer "Encyclopedia of Chemical Technology," (2nd ed.), vol. 21, page 321, Interscience, New York (1970). By another well-known conversion technique, ethylidene diacetate can be transformed into acetic anhydride plus acetaldehyde; see Kirk-Othmer "Encyclopedia of Chemical Technology," (2nd ed.), vol. 8, pages 410-413, Interscience, New York (1965). Reference is also made to U.S. Pat. No. 2,425,389 as indicative of the flexibility of ethylidene diacetate as a chemical intermediate.
Heretofore, however, the potential of ethylidene diacetate as a chemical intermediate has been severely limited by an absence of economic techniques for its preparation from readily available, inexpensive raw materials. One technique for ethylidene diacetate production involves the reaction of acetaldehyde and acetic anhydride to produce ethylidene diacetate as an intermediate for the production of vinyl acetate, a process which has been employed to a limited extent on a commercial scale; see "Hydrocarbon Process." 44 (11), 287 (1965). Another technique has involved the reduction of acetic anhydride with hydrogen; see Fenton, U.S. Pat. No. 3,579,566.
In consequence ethylidene diacetate's potential as a chemical intermediate has not been realized since its manufacture has involved the utilization of quite expensive raw materials which are today in short supply. In further consequence modern chemical technology has focused on the utilization of ethylene as the raw material for the production of acetic anhydride, acetaldehyde, vinyl acetate, and acetic acid. Ethylene production, of course, is contingent upon the use of petroleum fractions which are equally in short supply and not readily producible directly from carbon itself or from methane.
The utilization of non-petroleum based raw materials for the production of materials commercially derived from ethylene, such as the four enumerated above, has been and is today the subject of much research primarily focused upon the employment of carbonylation techniques, i.e., the reaction of carbon monoxide (with or without the concurrent presence of hydrogen) with organic materials. By such carbonylation techniques, a variety of materials have been produced successfully, at least upon a laboratory scale. Much of the early work in this area is summarized in Reppe, "Acetylene Chemistry," PB Report-18852-s, Charles A. Meyer & Co., Inc. (translator), at pages 162 et seq. (1949). However, in none of this early work was there any indication that ethylidene diacetate could be obtained by carbonylation techniques. In later work, in for example, Reppe et al., U.S. Pat. No. 2,727,902, methanol, carbon monoxide, and hydrogen were reacted under carbonylation conditions to yield "acetaldehyde dimethyl acetal," which is more commonly known as ethylidene dimethyl ether; see Merck Index, 8th ed., page 374, Merck & Co., New Jersey (1968). Indeed, acetals are the only gem-type compounds heretofore known as being capable of being produced by carbonylation techniques; see Butter, U.S. Pat. No. 3,285,948, and Schultz, U.S. Pat. No. 3,689,533.
In summary, though much effort has been devoted to research in the area of carbonylation reactions, in no known instance have carbonylation techniques heretofore been disclosed for preparation of ethylidene diacetate despite the obvious desirability of this material as a chemical intermediate.